Comet IRAS–Araki–Alcock (formal designation C/1983 H1, formerly 1983 VII) is a long-period comet that, in 1983, made the closest approach to Earth, about 0.0312 AU (4,670,000 km; 2,900,000 mi), of any comet in 200 years; only Lexell's Comet, in 1770, and 55P/Tempel-Tuttle, in 1366, are thought to have come closer.[3][4] (The small comet P/1999 J6 (SOHO) passed about 0.012 AU (1,800,000 km; 1,100,000 mi) from Earth on 1999-Jun-12.[5] and a small fragment of 252P/LINEAR called P/2016 BA14 passed at a distance of 0.0237 AU (3,550,000 km; 2,200,000 mi) on 22 March 2016[6])

During the closest approach the comet appeared as a circular cloud about the size of the full moon, having no discernible tail, and shining at a naked eye magnitude of 3–4. It swept across the sky at an incredible speed of some 30 degrees per day.

It is a long-period comet, with an orbital period of around 970 years,[1] and is the parent comet of the minor Eta Lyridmeteor shower.[9] This shower's radiant lies between Vega and Cygnus and produces 1 or 2 meteors an hour in mid-May with a peak between May 9 and May 11.

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Comet IRAS–Araki–Alcock is thought to have made the closest approach to Earth in 1983, about 0.0312 AU (4,670,000 km; 2,900,000 mi). This would make it he closest approach up to that time of any comet in 200 years; only Lexell's Comet, in 1770, and 55P/Tempel-Tuttle, in 1366, are thought to have come closer.[3][4] The small comet P/1999 J6 (SOHO) passed about 0.012 AU (1,800,000 km; 1,100,000 mi) from Earth on 1999-Jun-12.[5] and what was though to be a small fragment of 252P/LINEAR called P/2016 BA14 passed at a distance of 0.0237 AU (3,550,000 km; 2,200,000 mi) on 22 March 2016[6] However, when observed during its flyby it BA14 was much larger than expected, going from over 100 meters to 1 km in size estimate and one reason for this it was found to be extremely dark.

The comet BA14 was calculated to have reflected only 2–3 percent of visible light, based on observations with the NASA Infrared Telescope Facility (a ground-based optical infrared telescope).[10]